I got my hands on John the Ripper and I know some parameters that will help narrow down the possible passwords. I just have no idea what file I'm supposed to tell john the ripper (or any brute force program) to attack.

John the Ripper is for finding the logon password for user accounts, it doesn't decrypt encrypted drives.

There ae tools to decrypt the encrypted drive but they requie the password to be in memory on the host mac system. They are also very expensive.Passware http://www.lostpassword.com apparently have products that can do this.